Python | Method Overloading

Like other languages (for example method overloading in C++) do, python does not supports method overloading by default. But there are different ways to achieve method overloading in Python.

The problem with method overloading in Python is that we may overload the methods but can only use the latest defined method.

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# First product method.
# Takes two argument and print their
# product
def product(a, b):
    p = a * b
    print(p)
      
# Second product method
# Takes three argument and print their
# product
def product(a, b, c):
    p = a * b*c
    print(p)
  
# Uncommenting the below line shows an error    
# product(4, 5)
  
# This line will call the second product method
product(4, 5, 5)

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Output:

100

In the above code we have defined two product method, but we can only use the second product method, as python does not supports method overloading. We may define many method of same name and different argument but we can only use the latest defined method. Calling the other method will produce an error. Like here calling product(4, 5) will produce an error as the latest defined product method takes three arguments.

Thus, to overcome the above problem we can use different ways to achieve the method overloading.



Method 1 (Not The Most Efficient Method):

We can use the arguments to make the same function work differently i.e. as per the arguments.

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# Function to take multiple arguments
def add(datatype, *args):
  
    # if datatype is int
    # initialize answer as 0
    if datatype =='int':
        answer = 0
          
    # if datatype is str
    # initialize answer as ''
    if datatype =='str':
        answer =''
  
    # Traverse through the arguments
    for x in args:
  
        # This will do addition if the 
        # arguments are int. Or concatenation 
        # if the arguments are str
        answer = answer + x
  
    print(answer)
  
# Integer
add('int', 5, 6)
  
# String
add('str', 'Hi ', 'Geeks')

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Output:

11
Hi Geeks

The problem with above code is that is makes code more complex with multiple if/else statement and is not the desired way to achieve the method overloading.

Method 2 (Efficient One):

By Using Multiple Dispatch Decorator

Multiple Dispatch Decorator Can be installed by:

pip3 install multipledispatch
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from multipledispatch import dispatch
  
#passing one parameter
@dispatch(int,int)
def product(first,second):
    result = first*second
    print(result);
  
#passing two parameters
@dispatch(int,int,int)
def product(first,second,third):
    result  = first * second * third
    print(result);
  
#you can also pass data type of any value as per requirement
@dispatch(float,float,float)
def product(first,second,third):
    result  = first * second * third
    print(result);
  
  
#calling product method with 2 arguments
product(2,3,2) #this will give output of 12
product(2.2,3.4,2.3) # this will give output of 17.985999999999997

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Output:

12
17.985999999999997

In Backend, Dispatcher creates an object which stores different implementation and on runtime it selects the appropriate method as the type and number of parameters passed.




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